Flexural weakening-shear strengthening (FWSS) technique for the seismic retrofit of RC frames: Experimental study

The strong column-weak beam hierarchy has been widely accepted in the design of reinforced concrete (RC) frames for good seismic performance. In many existing RC frames designed according to previous codes, however, such a hierarchy was not enforced. To rectify this deficiency, a novel seismic retrofit method based on the flexural weakening-shear strengthening (FWSS) concept was proposed by the authors’ group for such frames. To verify the effectiveness of the FWSS technique, an experimental study comprising 8 full-scale RC beams with a web opening was carried out. The test results show that the proposed technique can substantially reduce the flexural capacity of the beam and in the meantime ensure a ductile beam response. More specifically, a web opening of appropriate size can effectively reduce the flexural capacity of a T-section beam, and FRP shear strengthening to avoid shear failure ensures a ductile response.